Table of contents

We present Atacama Large Millimeter/submillimeter Array observations at ≈100 GHz with 005 (3 pc) resolution of the kiloparsec-scale jet seen in the nearby Seyfert galaxy NGC 1068, and we report the presence of parsec-scale blobs at the head of the jet. The combination of the detected radio flux (≈0.8 mJy), spectral index (≈0.5), and blob size (≈10 pc) suggests a strong magnetic field of B ≈ 240 μG. Such a strong magnetic field most likely implies magnetic field amplification by streaming cosmic rays. The estimated cosmic-ray power of the jet may exceed the limit set by the star formation activity in this galaxy. This result suggests that even modest-power jets can increase the galactic cosmic-ray content while propagating through the galactic bulge.

In the first billion years after its formation, the Galaxy underwent several mergers with dwarf satellites of various masses. The debris of Gaia-Sausage/Enceladus (GSE), the galaxy responsible for the last significant merger of the Milky Way, dominates the inner halo and has been suggested to be the progenitor of both the Hercules-Aquila Cloud (HAC) and Virgo Overdensity (VOD). We combine SEGUE, APOGEE, Gaia, and StarHorse distances to characterize the chemodynamical properties and verify the link between HAC, VOD, and GSE. We find that the orbital eccentricity distributions of the stellar overdensities and GSE are comparable. We also find that they have similar, strongly peaked, metallicity distribution functions, reinforcing the hypothesis of common origin. Furthermore, we show that HAC and VOD are indistinguishable from the prototypical GSE population within all chemical-abundance spaces analyzed. All these evidences combined provide a clear demonstration that the GSE merger is the main progenitor of the stellar populations found within these halo overdensities.

We present the discovery of a wide retrograde moving group in the disk plane of the Milky Way using action-angle coordinates derived from the Gaia DR3 catalog. The structure is identified from a sample of its members that are currently almost at the pericenter of their orbit and are passing through the solar neighborhood. The motions of the stars in this group are highly correlated, indicating that the system is probably not phase mixed. With a width of at least 1.5 kpc and with a probable intrinsic spread in metallicity, this structure is most likely the wide remnant of a tidal stream of a disrupted ancient dwarf galaxy (age ∼12 Gyr, 〈[Fe/H]〉 ∼ −1.74). The structure presents many similarities (e.g., in energy, angular momentum, metallicity, and eccentricity) with the Sequoia merging event. However, it possesses extremely low vertical action J_z, which makes it unique even among Sequoia dynamical groups. As the low J_z may be attributable to dynamical friction, we speculate that these stars may be the remnants of the dense core of the Sequoia progenitor.

Companions at subarcsecond separation from young stars are difficult to image. However, their presence can be inferred from the perturbations they create in the dust and gas of protoplanetary disks. Here we present a new interpretation of SPHERE polarized observations that reveal the previously detected inner spiral in the disk of HD 100546. The spiral coincides with a newly detected ¹²CO inner spiral and the previously reported CO emission Doppler flip, which has been interpreted as the signature of an embedded protoplanet. Comparisons with hydrodynamical models indicate that this Doppler flip is instead the kinematic counterpart of the spiral, which is likely generated by an inner companion inside the disk cavity.

X-shaped radio galaxies (XRGs) produce misaligned X-shaped jet pairs and make up ≲10% of radio galaxies. XRGs are thought to emerge in galaxies featuring a binary supermassive black hole (SMBH), SMBH merger, or large-scale ambient medium asymmetry. We demonstrate that XRG morphology can naturally form without such special, preexisting conditions. Our 3D general-relativistic magnetohydrodynamic (GRMHD) simulation for the first time follows magnetized rotating gas from outside the SMBH sphere of influence of radius R_B to the SMBH of gravitational radius R_g at the largest scale separation, R_B/R_g = 10³, to date. Initially, our axisymmetric system of constant-density hot gas contains a weak vertical magnetic field and rotates in the equatorial plane of a rapidly spinning SMBH. We seed the gas with small-scale 2% level pressure perturbations. Infalling gas forms an accretion disk, and the SMBH launches relativistically magnetized collimated jets reaching well outside R_B. Under the pressure of the infalling gas, the jets intermittently turn on and off, erratically wobble, and inflate pairs of cavities in different directions, resembling an X-shaped jet morphology. Synthetic X-ray images reveal multiple pairs of jet-powered shocks and cavities. Large-scale magnetic flux accumulates on the SMBH, becomes dynamically important, and leads to a magnetically arrested disk state. The SMBH accretes at 2% of the Bondi rate ($\dot{M}\simeq 2.4\times {10}^{-3}{M}_{\odot }\,{\mathrm{yr}}^{-1}$ for M87*) and launches twin jets at η = 150% efficiency. These jets are powerful enough (P_jets ≃ 2 × 10⁴⁴ erg s⁻¹) to escape along the SMBH spin axis and end the short-lived intermittent jet state, whose transient nature can account for the rarity of XRGs.

Protostellar outflows are one of the most outstanding features of star formation. Observational studies over the last several decades have successfully demonstrated that outflows are ubiquitously associated with low- and high-mass protostars in solar-metallicity Galactic conditions. However, the environmental dependence of protostellar outflow properties is still poorly understood, particularly in the low-metallicity regime. Here we report the first detection of a molecular outflow in the Small Magellanic Cloud with 0.2 Z_⊙, using Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of 0.1 pc toward the massive protostar Y246. The bipolar outflow is nicely illustrated by high-velocity wings of CO(3–2) emission at ≳15 km s⁻¹. The evaluated properties of the outflow (momentum, mechanical force, etc.) are consistent with those of the Galactic counterparts. Our results suggest that the molecular outflows, i.e., the guidepost of the disk accretion at the small scale, might be universally associated with protostars across the metallicity range of ∼0.2–1 Z_⊙.

Super-metal-rich (SMR) stars in the solar neighborhood are thought to be born in the inner disk and come to their present location by radial migration, which is most intense at the corotation resonance (CR) of the Galactic bar. In this work, we show evidence for the CR origin of SMR stars in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and Gaia by detecting six ridges and undulations in the ϕ versus L_z space coded by median V_R, following a similar slope of −8 km s⁻¹ kpc deg⁻¹. The slope is predicted by Monario et al.'s model for CR of a large and slow Galactic bar. For the first time, we show the variation in the angular momentum with azimuths from −10° to 20° for two outer and broad undulations with negative V_R around − 18 km s⁻¹ following this slope. The wave-like pattern with large amplitude outside CR and a wide peak of the second undulation indicate that minor merger of the Sagittarius dwarf galaxy with the disk might play a role besides the significant impact of the CR of the Galactic bar.

We report the serendipitous discovery of an [O iii] λλ4959/5007 and Hα line emitter in the Epoch of Reionization (EoR) with the James Webb Space Telescope (JWST) commissioning data taken in the NIRCam wide-field slitless spectroscopy (WFSS) mode. Located ∼55'' away from the flux calibrator P330-E, this galaxy exhibits bright [O iii] λλ4959/5007 and Hα lines detected at 3.7σ, 9.9σ, and 5.7σ, respectively, with a spectroscopic redshift of z = 6.112 ± 0.001. The total Hβ+[O iii] equivalent width is 664 ± 98 Å (454 ± 78 Å from the [O iii] λ5007 line). This provides direct spectroscopic evidence for the presence of strong rest-frame optical lines (Hβ+[O iii] and Hα) in EoR galaxies as inferred previously from the analyses of the Spitzer/IRAC spectral energy distributions (SEDs). Two spatial and velocity components are identified in this source, possibly indicating that this system is undergoing a major merger, which might have triggered the ongoing starburst with strong nebular emission lines over a timescale of ∼2 Myr, as our SED modeling suggests. The tentative detection of He iiλ4686 line (1.9σ), if real, may indicate the existence of very young and metal-poor star-forming regions with a hard UV radiation field. Finally, this discovery demonstrates the power and readiness of the JWST/NIRCam WFSS mode, and marks the beginning of a new era for extragalactic astronomy, in which EoR galaxies can be routinely discovered via blind slitless spectroscopy through the detection of rest-frame optical emission lines.

The interactions between a relativistic magnetized collisionless shock and dense clumps have been expected to play a crucial role in magnetic field amplification and cosmic-ray acceleration. We investigate this process using two-dimensional Particle-In-Cell (PIC) simulations, for the first time, where the clump size is much larger than the gyroradius of the downstream particles. We also perform relativistic magnetohydrodynamic (MHD) simulations for the same condition, to see the kinetic effects. We find that particles escape from the shocked clump along magnetic field lines in the PIC simulations, so that the vorticity is lower than that in the MHD simulations. Moreover, in both the PIC and MHD simulations, the shocked clump quickly decelerates because of relativistic effects. Owing to the escape and the deceleration, the shocked clump cannot amplify the downstream magnetic field in relativistic collisionless shocks. This large-scale PIC simulation opens a new window to understanding large-scale behaviors in collisionless plasma systems.

Gamma-ray bursts (GRBs) have been phenomenologically divided into long- and short-duration populations, generally corresponding to collapsar and compact merger origins, respectively. Here, we collect three unique bursts, GRBs 060614, 211211A, and 211227A, all of which are characterized by a long-duration main emission (ME) phase and a rebrightening extended emission (EE) phase, to study their observed properties and their potential origins as neutron star–black hole (NSBH) mergers. NS-first-born (BH-first-born) NSBH mergers tend to contain fast-spinning (nonspinning) BHs that more easily (hardly) allow tidal disruption to occur, while (without) forming electromagnetic signals. We find that NS-first-born NSBH mergers can well interpret the origins of these three GRBs, supported by the following. (1) Their X-ray MEs and EEs show unambiguous fallback accretion signatures, decreasing as ∝ t^−5/3, which might account for their long durations. The EEs could result from the fallback accretion of r-process heating materials, which is predicted to occur after NSBH mergers. (2) The beaming-corrected local event-rate density for these types of merger-origin long-duration GRBs is ${{ \mathcal R }}_{0}\sim {2.4}_{-1.3}^{+2.3}\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$, consistent with that of NS-first-born NSBH mergers. (3) Our detailed analysis of the EE, afterglow, and kilonova of the recent high-impact event GRB 211211A reveals that it could be a merger between a $\sim {1.23}_{-0.07}^{+0.06}\,{M}_{\odot }$ NS and a $\sim {8.21}_{-0.75}^{+0.77}\,{M}_{\odot }$ BH, with an aligned spin of ${\chi }_{\mathrm{BH}}\sim {0.62}_{-0.07}^{+0.06}$, supporting an NS-first-born NSBH formation channel. A long-duration burst, with a rebrightening fallback accretion signature after the ME, and a bright kilonova, might be commonly observed features for on-axis NSBH mergers. We estimate the multimessenger detection rate between gravitational waves, GRBs, and kilonova emissions from NSBH mergers in O4 (O5) to be ∼0.1 yr⁻¹ (∼1 yr⁻¹).

Observations and simulations have demonstrated that star formation in galaxies must be actively suppressed to prevent the formation of overly massive galaxies. Galactic outflows driven by stellar feedback or supermassive black hole accretion are often invoked to regulate the amount of cold molecular gas available for future star formation but may not be the only relevant quenching processes in all galaxies. We present the discovery of vast molecular tidal features extending up to 64 kpc outside of a massive z = 0.646 post-starburst galaxy that recently concluded its primary star-forming episode. The tidal tails contain (1.2 ± 0.1) × 10¹⁰M_⊙ of molecular gas, 47% ± 5% of the total cold gas reservoir of the system. Both the scale and magnitude of the molecular tidal features are unprecedented compared to all known nearby or high-redshift merging systems. We infer that the cold gas was stripped from the host galaxies during the merger, which is most likely responsible for triggering the initial burst phase and the subsequent suppression of star formation. While only a single example, this result shows that galaxy mergers can regulate the cold gas contents in distant galaxies by directly removing a large fraction of the molecular gas fuel, and plausibly suppress star formation directly, a qualitatively different physical mechanism than feedback-driven outflows.

We present two homologous quasi-periodic fast-mode propagating (QFP) wave trains excited by two small-scale filament eruptions nearby a sunspot on 2017 September 12. By using observations from several ground-based and space-based instruments, it is found that the eruptions of two small-scale filaments resulted in some accompanying solar phenomena/activities (such as radio bursts, GOES C-class flares, coronal bright fronts, and QFP wave trains). The QFP wave trains run behind the main coronal bright fronts with a constant propagating speed of about 800 km s⁻¹, while two main coronal bright fronts traveled away from the flare kernel obeying the power-law functions of $S(t)=894.9\ast {\left(t-7.43\right)}^{0.60}+76.8$ and S(t) = 705.3 ∗ (t − 19.12)^0.47 + 57.5, respectively. The period of the first QFP wave train was estimated to be about 59 s, while the second QFP wave train has two periods of about 70 and 37 s. On the other hand, the intensity peaks of 94 and 335 Å passbands in the flare kernel exhibit some perturbations during the occurrences of the QFP wave trains. With the wavelet analysis and their synchronization, these perturbations and the QFP wave trains are tightly related phenomena, which suggests that they have a common exciting mechanism. Furthermore, we find that the emissions of the intensity peak mainly originate from the one footpoint of flare loops during the occurrence of the QFP wave trains. According to the above features, we conclude that the QFP wave trains are excited in the energy release process associated with magnetic reconnection and are closely related to the outflow of the magnetic reconnection.

We present a detailed analysis of a reflecting intensity perturbation in a large coronal loop that appeared as a sloshing oscillation and lasted for at least one and a half periods. The perturbation is initiated by a microflare at one footpoint of the loop, propagates along the loop, and is eventually reflected at the remote footpoint where significant brightenings are observed in all of the Atmospheric Imaging Assembly extreme-ultraviolet channels. This unique observation provides us with the opportunity to better understand not only the thermal properties and damping mechanisms of the sloshing oscillation but also the energy transfer at the remote footpoint. Based on differential emission measures analysis and the technique of coronal seismology, we find that (1) the calculated local sound speed is consistent with the observed propagation speed of the perturbation during the oscillation, which is suggestive of a slow magnetoacoustic wave; (2) thermal conduction is the major damping mechanism of the wave but an additional damping mechanism such as anomalous enhancement of compressive viscosity or wave leakage is also required to account for the rapid decay of the observed waves; (3) the wave produced a nanoflare at the remote footpoint, with a peak thermal energy of ∼10²⁴–10²⁵ erg. This work provides a consistent picture of the magnetoacoustic wave propagation and reflection in a coronal loop, and reports the first solid evidence of a wave-induced nanoflare. The results reveal new clues for further simulation studies and may help with solving the coronal heating problem.

The James Webb Space Telescope (JWST) Early Release Observations (EROs) is a set of public outreach products created to mark the end of commissioning and the beginning of science operations for JWST. Colloquially known as the "Webb First Images and Spectra," these products were intended to demonstrate to the worldwide public that JWST is ready for science, and is capable of producing spectacular results. The package was released on 2022 July 12 and included images and spectra of the galaxy cluster SMACS J0723.3-7327 and distant lensed galaxies, the interacting galaxy group Stephan's Quintet, NGC 3324 in the Carina star-forming complex, the Southern Ring planetary nebula NGC 3132, and the transiting hot Jupiter WASP-96b. This paper describes the ERO technical design, observations, and scientific processing of data underlying the colorful outreach products.

The hot (>10⁶ K) phase of the circumgalactic medium (CGM) contains a large fraction of baryons in galaxies. It also retains signatures of the processes that shaped the galaxies, such as feedback from active galactic nuclei and supernovae, and offers a uniquely powerful way to constrain theoretical models of feedback. It is, however, notoriously difficult to detect. By stacking 2643 optically selected galaxies in the eROSITA Final Equatorial Depth Survey, we present spatially resolved properties of the extended CGM in both star-forming and quiescent galaxies spanning an order of magnitude in stellar mass. We mask out resolved point sources and galaxy groups/clusters and model the contribution from X-ray binaries and the hot interstellar medium, producing accurate radial profiles. We compare the profiles to mock X-ray observations of galaxy stacks in the IllustrisTNG100 and EAGLE cosmological simulations. We detect extended emission from both the high-mass ($10.7\lt \mathrm{log}({M}_{* }/{M}_{\odot })\lt 11.2$) and low-mass ($10.2\lt \mathrm{log}({M}_{* }/{M}_{\odot })\lt 10.7$) galaxy stacks. Galaxies have somewhat more luminous CGM between 10 and 100 kpc if they are more massive or star-forming. However, the luminosity increases more slowly with stellar mass than predicted in simulations. Simulated quenched galaxies are dimmer than observed, suggesting that they rely too heavily on CGM ejection for quenching. Star-forming galaxies are observed to have flatter and more extended profiles than in simulations, suggesting underefficient stellar feedback models. Our results highlight the need to modify future prescriptions of galaxy feedback models.